Things used to be simpler. Indoors, events producers stacked videowall ‘cubes’ – long boxes with a projector at one end and a screen at the other – to create large displays. Outdoors, they used devices such as Sony Jumbotron or, later, LED displays made up from multiple panels. But that was at least a decade ago. Now, there are many more technical options available for use in the videowall/large screen display market.

Conventional, stackable videowall cubes (mostly with LCD or DLP projects and mirrors to fold the projection path and make them more compact) are still available. Rigs using multiple projectors and mirrors are in common use. Flat screen displays with very narrow bezels can be mounted together to form a large, but very thin, indoor videowall. Indoor LED panels using high resolution displays are becoming increasingly available and affordable, while very large screen LED displays at resolutions ranging from 4mm to 25mm or 35mm are being used everywhere – in shop windows, on transportation systems, in tv studios and at sporting events.

And development hasn’t stopped. This year’s ISE show saw the launch of cheaper and lighter indoor LED screens such as the Nanolumens offering and the first showing of production versions of genuinely new technology screens such as the Mitsubishi large screen OLED displayand Prysm’s laser phosphor display (LPD) technology. Christie’s stackable MicroTiles system – in principle, a small videowall cube – was also much in evidence and, a year after launch, it is being used in serious commercial applications.

As well as changes in technology, different application sectors now have clear requirements of their own. For example, the control room market, digital signage, public display, rock concerts and sports venues now have individual ‘takes’ on the technology that is right for them.

Projection videowall
There’s still a place for videowall cubes with a projector in the back and a screen on the front but the main market for such products in now in control rooms which require very high resolution displays (up to UXGA or above) and can be operated 24×7 with very low failure rates and long periods between lamp changes. Front access via a hinged screen is usually provided for maintenance purposes.

Rear projection (RP) cubes developed for the needs of the control room market also feature sophisticated electronic set-up software to manage colour balance and brightness across the videowall. They use image processing and switching to manage the supply of different information (such as the images from traffic or surveillance cameras) to different ‘windows’ on the wall.

RP systems are also extensively used as a tv news studio backdrop but the more sophisticated broadcasters usually use a multi-projector rig on a seamless screen, rather than cubes. In this application, key requirements include colour and brightness/contrast balance between screens as well as very accurate picture alignment.

Flat screens
In some control room applications large flat screen videowall cubes are being used to replace RP units. Many of the same requirements – including screen life and between-screen picture balancing – apply and some manufacturers are now replacing the fluorescent backlights usually used with LCD screens of 60in diagonal or more with LED lighting to achieve longer backlight life between replacement as well as lower power consumption.

Generally, the flat screens being used in control rooms are larger and less bright than those used for videowalls at exhibitions, in public areas and in retail environments.

In these applications – which include the events rental market – there is now increased availability of thin bezel or even bezel-less LCD and plasma screens that can be assembled into a videowall.

As well as thin-bezel screens with surround thicknesses of 2-6mm or less, edge-lit screens using LED backlighting are now becoming available. Their advantages include reduced depth, as well as allowing visually join-free walls to be assembled.

There are a range of options for image control on flat screen videowalls. Some manufacturers offer their own software, which takes the image and distributes it across a number of colour-balanced screens, but many users – especially in live events and control rooms – still prefer to use external controllers.

LED developments
The major divide in the LED screenmarket is still between high resolution screens designed for indoor use, generally with 4-10mm resolution (based on the gaps between pixels) and outdoor screens for use in transport terminals and at sporting events and concerts.

Most buying decisions are based on an equation which seeks to balance the cost of high pixel density screens with viewing distance, but other considerations also apply. In retail markets, for example, high brightness LED screens are being used in street-facing applications instead of videowalls or large plasma displays, but deploying 4mm or 6mmLED screens has demanded deep pockets.

The outdoor market has also matured, with concerts making increasing use of flexible screens and low-resolution displays that combine the roles of lighting and video replay. In the sports sector it’s often the screen mounting structure that is the main differentiator, with stadiums the increasing use of fixed installations, while other events’ focus is on speed of erection and transportability.

Prospects
As technologies become more ‘productionised’ OLED, LPD, edge-lit flat panels and MicroTiles will increase the use of videowalls in retail, signage and public display, especially once higher resolution source material becomes available.

The London Olympics will deploy more outdoor LED screens than ever before. But there’s one project I can’t wait to see – a see-through videowall using the semi-transparent edge-lit flat screens that LG showed at ISE.